1. Field of the Invention
The present disclosure relates to a vacuum interrupter for performing an arc extinguishing operation in a vacuum circuit breaker, and more particularly, to a vacuum interrupter of the vacuum circuit breaker for increasing a radial magnetic field having an effect on an arc driving force.
2. Description of the Related Art
In general, a vacuum interrupter in a vacuum circuit breaker is a core extinguishing device applied to a vacuum circuit breaker, a vacuum switch, a vacuum contactor, and the like to interrupt a load current or fault current in a power system. The vacuum circuit breaker, which performs the role of controlling electric power transmission and protecting a power system, has a lot of advantages, such as a large breaking capacity, a high reliability and an enhanced stability, a superior mountability even in a small installation space, and the like, and thus the application area has been expanded to include medium voltages and high voltages. Furthermore, the breaking capacity of the circuit breakers has been also increased in proportion to the increased size of industrial facilities.
The vacuum interrupter in a vacuum circuit breaker operates by using a magnetic field generated by a current flowing through an inherent electrode structure therein at the time of interrupting a fault current. The vacuum interrupter may be largely divided into an axial magnetic field (AMF) type and a radial magnetic field (RMF) type based on the method of generating a magnetic field.
The radial magnetic field type may represent a method of allowing an arc being shrunken by a pinch effect to move while at the same time generating the arc, thereby preventing the damage of the contacts that can occur when a high-temperature arc is constricted between the contacts.
The vacuum interrupter may be advantageous in the aspect of controlling an arc when it has a high arc driving force. The arc driving force may be generated by an interaction between a current density (J) of the current flowing through the arc and a magnetic flux density (B) of the magnetic field generated by a current flowing through the contact shape on its component (F=J×B, where the arc driving force acts in a direction perpendicular to a plane made by two vectors, which are referred to as a current density and a magnetic flux density). Accordingly, the arc driving force can be increased when increasing the current density or magnetic flux density.
FIG. 1 is a longitudinal cross-sectional view illustrating a vacuum interrupter in the related art.
Referring to FIG. 1, in a vacuum interrupter in the related art, an insulated container 1 is sealed by a stationary side seal cap 2 and a movable side seal cap 3, a stationary electrode 4 and a movable electrode 5 are provided to face each other in the insulated container 1 so as to be brought into contact with each other, an inner shield 6 is provided to accommodate a space between the stationary electrode 4 and the movable electrode 5, a stationary shaft 4a of the stationary electrode 4 is fixed to and combined with the stationary side seal cap 2 to be connected to the outside thereof, and a movable shaft 5a of the movable electrode 5 is slidably combined with the movable side seal cap 3 to be connected to the outside thereof.
Furthermore, a flexible tube shield 7 is fixed to and combined with the movable shaft 5a of the movable electrode 5, and a flexible tube 8 is provided between the flexible tube shield 7 and the movable flange 3 in such a manner that the movable electrode 5 and movable shaft 5a can be moved in a sealed state within the insulated container 1.
The inner shield 6 is located at a symmetrical position when both electrodes 4, 5 are completely opened, and metal vapor dispersed at the time of generating an arc during the operation of breaking the circuit is adhered thereto, thereby preventing a dielectric strength from being reduced when metal vapor is attached to an inner surface of the insulated container 1.
The foregoing vacuum interrupter in the related art may generate a magnetic field in a radial direction (in a radially emitted direction from the moving direction of the movable electrode) by the stationary electrode 4 and movable electrode 5, and a current flowing through an arc for electrically connecting the two electrodes 4, 5 to each other during the generation of the arc. The magnetic field receives a force due to an interaction with a current flowing from the stationary electrode 4 to the movable electrode 5, and the electrodes are located at the fixed positions, respectively, but the arc moves when receiving the force. Here, the moving direction of the arc should be a direction perpendicular to a plane made by two vectors, which are referred to as a current and a magnetic field, namely, a circumferential direction (i.e., a direction rotated around the shaft) on the basis of a contact point such as an electromagnetic force acting on fluid (a direction perpendicular to the paper surface in the drawing).
However, in the foregoing vacuum interrupter in the related art, part of the arc may not flow in a direction perpendicular to a plane made by a current and a magnetic field (also referred to as “a pure horizontal direction”) but flow in the circumference of the pure horizontal direction, namely, an obliquely-diffused direction in the drawing (also referred to as “a non-pure horizontal direction”). The non-pure horizontal direction may be a cause of deteriorating an arc driving force as well as a loss due to a kind of leakage flux compared to a radial magnetic field in the pure horizontal direction contributing to the arc driving force.